The functions performed by some currently available medical electronic devices can be altered or controlled by accepting various electronic modules that electrically interconnect with the electronic device. For example, heart rate monitors may be expanded to provide blood pressure data upon addition of an appropriate blood pressure monitoring module. Designing such modules to provide upgradability of the medical electronic device is not particularly problematic with stationary devices. When medical electronic devices are designed to be portable, however, problems arise. For example, the portable medical device must generally be compact and lightweight to allow it to be readily portable. As a result, any modules for the portable medical device must also, be compact and lightweight.
In a medical electronic device accepting plug-in modules to control its functions,, it is generally desirable to make the modules quick and easy to install and remove from the electronic device so that the functions performed by the medical device can be easily changed. However, making the module so that it is easily removable has a tendency to make the module easily dislodged by impact shocks. This problem is normally not too serious for stationary medical electronic devices. However, portable electronic: devices are often handled roughly or dropped during active use. If the portable medical electronic device is to accept electronic modules, these modules must be securely retained by the electronic device. Any impact shock that the medical electronic: device may receive must not dislodge or disconnect the electronic module from the device.
One approach to solving this impact shock problem would be for the module to tightly fit into the medical electronic device so that it is not able to move when subjected to impact shocks. However, to prevent the module from electrically disconnecting from the electronic device when subjected to impact shock, close, tight tolerances between the module and a bay in the electronic device accepting the module are generally necessary. These tight tolerances generally cannot be achieved using relatively inexpensive, high volume production techniques. As a result, plug-in modules for portable electronic devices would be relatively expensive.
If the portable electronic device is to be used outdoors or in a variety of environmental conditions, the device must be environmentally sound. It must generally be able to resist penetration of moisture or other fluids into the electronics of the device. Most modular systems provide bays or ports which receive the modules. These bays are generally not environmentally sound because water may easily penetrate through ports in these bays into the interior of the electronic device. To maintain environmental integrity, conventional medical electronic devices that are designed to be portable must eliminate the bay and allow upgradability only internal to the device. Namely, the electronic device must be partially disassembled, the new electronics coupled to the internal electronics in the device, and then the electronic device must be reassembled. This assembly/disassembly does not permit simple upgradability by an average user of the device through the use of a module. Consequently, current portable medical electronic devices that are environmentally sound may not be upgradable through the use of modules.
Overall, no portable medical electronic device of which the inventors are aware avoids impact shock and other environmental hazards inherent in a portable device and yet allows the function of the device to be readily changed or upgraded through the use of easily installed modules.